Routing circuitry is utilized to transfer a signal from one circuit element to another circuit element within an integrated circuit. The routing circuitry may include a pass gate transistor that gates the signal transmission. The pass gate transistor is controlled by a control signal, which is stored within a configuration random-access memory (CRAM) cell.
Generally, a pass gate transistor is an n-channel transistor (i.e., n-channel metal oxide semiconductor (NMOS) transistor). An n-channel transistor exhibits better charge mobility and conductive characteristics than a p-channel transistor. It is generally desired that a gate terminal of an n-channel pass gate transistor receive a voltage greater than a voltage level of a data signal received at its source-drain terminal by at least one threshold voltage level (Vt) but less than a maximum voltage level allowed between any two transistor junctions (VMAX). Such voltage levels supplied to the gate terminal may overdrive the n-channel pass gate transistor.
In older semiconductor process technologies, the VMAX tends to be only slightly greater than the standard voltage level. Therefore, although the n-channel pass gate transistor can be overdriven, other optimizations to the pass gates are restricted. However, with newer semiconductor process technologies, the VMAX headroom is increased. This provides much more flexibility in terms of designing a pass gate circuit and more room for optimization.